My excel spreadsheet won't calculate formulas anymore. Help

[csadler]

My spreadsheet for calculating our employee hours used to work just fine.
Something happened and now it doesn't calculate. This seems to be a problem
with excel as my workbook has several sheets with exact same formulas. None
of them work. Could it be a bug? or a virus, possibly downloaded from
internet excel file? I was experimenting with excel formulas calculating
hours and overtime hours. And I did a download, but not into this
spreadsheet. Thanks for any help

 

[Eduardo]

Hi,
check tha the calculation method has not been changed from automatic to manual
Microsoft button, Excel options, formulas,Calculation options

if this helps please click yes, thanks

 

[bug fongers]

That fixed it for me, but how on earth did it get changed to begin with?
Thank you!